1. Field of the Invention
This invention relates to an expansion valve that adiabatically expands high-pressure refrigerant introduced therein to deliver the same to an evaporator, and includes a pressure sensor for sensing the pressure of the high-pressure refrigerant.
2. Description of the Related Art
Conventionally, a box-shaped expansion valve is known which has a valve portion for adiabatically expanding high-pressure refrigerant introduced therein to deliver the same to an evaporator, and a refrigerant passage for allowing refrigerant from the evaporator to pass therethrough, formed in the same body block, and includes a power element for sensing the temperature and pressure of the refrigerant at an outlet port of the evaporator. The expansion valve of this type is generally configured such that a valve element of the valve portion is urged by the power element for sensing the temperature and pressure of refrigerant at the outlet port of the evaporator to thereby control a valve travel of the valve.
Further, a refrigeration cycle has a pressure switch or a pressure sensor arranged therein, for detecting the pressure of refrigerant with a view to performing optimum cooling and heating operations. The above pressure switch or the pressure sensor has generally been attached to a refrigerant piping by way of a joint. Recently, however, a plurality of components are being integrally modularized to simplify the whole construction of the refrigeration cycle. This results in limited locations in the refrigeration cycle where the pressure switch or the pressure sensor can be freely attached. To cope with this inconvenience, it is now a practice to mount the pressure switch or the pressure sensor integrally with a portion of the expansion valve where the high pressure is introduced, for detection of the pressure of condensed liquid refrigerant, instead of attaching the pressure switch or the pressure sensor to a refrigerant piping.
As shown in FIG. 3, in the conventional expansion valve provided with the pressure sensor, the valve element 8 for controlling the flow rate of refrigerant is urged in a valve-closing direction by a compression coil spring 9 which is arranged within an opening 2a formed in the body block 2 such that the opening 2a has one end open to the outside air. Further, the compression coil spring 9 has a fixed end thereof received by an adjusting screw 10 screwed into a thread 2b formed in an inner wall of the opening 2a. A set value at which the valve element 8 of the expansion valve starts to open is adjusted by adjusting the amount of screwing of the adjusting screw 10 to change the urging force of the compression coil spring 9.
Further, the pressure sensor 22 is fitted at an open end-side portion of the opening 2a, for detecting the pressure of refrigerant within a high-pressure refrigerant passage. Mounted between the pressure sensor 22 and the opening 2a is a sealing O ring 22e for preventing leakage of refrigerant from the opening 2a. 
As described above, the conventional expansion valve is constructed such that the adjusting screw 10 and the pressure sensor 22 are sequentially mounted in the opening 2a. Therefore, the assembly work of the valve is troublesome and parts cost cannot be reduced.
An object of the invention is to provide an expansion valve including a pressure sensor which enables reduction of parts cost.
To attain the above object, there is provided an expansion valve that has a first passage for adiabatically expanding high-pressure refrigerant introduced therein to deliver the refrigerant to an evaporator, and a second passage through which refrigerant from the evaporator passes, formed in the same body block, characterized by comprising a valve element arranged in a manner opposed to a valve seat formed in an intermediate portion of the first passage, a power element for urging the valve element in directions of moving to and moving away from the valve seat according to a temperature and pressure of refrigerant in the low-pressure refrigerant passage, a compression coil spring for urging the valve element toward the valve seat, and a pressure sensor that is screwed into an opening of the body block, the opening being formed to communicate with a side of the first passage where the high-pressure refrigerant is introduced, such that the pressure sensor receives a fixed end of the compression coil spring on a side opposite to the valve element, for sensing pressure of the introduced high-pressure refrigerant, wherein the compression coil spring has load thereon adjusted by an amount of screwing of the pressure sensor.
The above and other objects, features and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the present invention by way of example.